442 



DISCOVERY REPORTS 



in the Cetacea by the similarity between the male and the female ligamenta lata and the 

 position of the testis. This " pseudo-hermaphroditism " reaches its maximum expression 

 in the Mammalia among the Rodents, but among the Ungulates it is also found. The 

 horse, donkey and zebra all have a Mullerian system developed as a long vagina mascu- 

 lina like that of the Narwhal, bifid at its tip ; while the goat and reindeer have long 

 Mullerian ducts like those of Mesoplodon. 



(v) The absence of seminal vesicles. Since there is no convincing evidence that the 

 small sacs described by various authors on the vasa deferentia really represent reduced 

 seminal vesicles, it may be assumed that the vesiculae seminales are not merely secondarily 

 absent from the Cetacean system. The absence of these organs may be assumed to be 

 more primitive than their presence, especially as they are absent in the Monotremes. 

 The Pinnipede Carnivores also lack seminal vesicles. 



The retraction of the penis into a penis sac by means of a pair of retractor penis 

 muscles is perhaps the only specialized character observable in the male genital system 

 of the Cetacea ; it relates the system to that of the stallion in which a similar pair of re- 

 tractor muscles is found and the penis becomes withdrawn into a sac in the inguinal region. 



After the above short comparative summary of the genital system of the Cetacea it 

 will be seen that, besides many extremely primitive characters indicating not necessarily 

 origin from, but affinity to some very primitive Insectivore-like mammal, the greatest 

 number of points show resemblance to the Ungulata, especially the Perissodactyles. As 

 pointed out by Anthony (1926) the Cetacea further resemble the Ungulata in having 

 a non-deciduate diffuse placenta; while the Carnivora, which show many points of 

 resemblance in their general anatomy to the Cetacea and which, on account of the 

 Creodont-like nature of the earliest fossil Zeuglodons, may claim affinity to the Cetacea, 

 have a deciduate zonary placenta. Further, while the Carnivora bear at least two young 

 at a time and frequently bear their young in large litters, the Ungulates and Cetacea bear 

 almost always a single young at a birth, and while the gestation period of the Carnivora is 

 short, that of the Cetacea and Ungulata is long (dog, 60 days ; cat, 56 days ; tiger and lion, 

 108 days ; horse, 347 days ; cow, 290 days ; deer, 284 days ; sheep, 1 50 days ; Balaenoptera, 

 10-12 months ; Orchitis, 12 months ; Delphinus delphis, 300 days). Anthony, who relates 

 the Cetacea to the early Condylarthra, suggests some such relationship as the following : 



Unknown Primitive Form 



First Condylarthra 



/ 



First Creodonts 



Condylarthra and 

 related forms 



Creodonta 



Perissodactyles 



/ 

 / 

 / 

 Artiodactyles 



\ 



Carnivores 



